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The backtrack option is specified in case it is needed, which is in this case because of the cast versus parenthesized expression in primary. Ooops. Just realized that the order of the alternatives is wrong. The primary will match the parenthesized expression before trying to cast. we need a way to figure this out.
The suffix rule has left recursive references to e sell those must be removed. The parse_expr rule invokes a suffix after having matched e already:
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